Tips On How To Obtain Defects-Free PCB's
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By: Giyora Kimhi, General Manager - Elcad Industried 
(91) Ltd.

The common solution to problems of defects in PCB's is 
first in the level of the software checking which is 
operated on CAM stations such as Orbotech's. During 
this check the Gerber files images are compared with 
the PCB Source file. This stage is commonly called "CAD 
Data Netlist Testing". The PCB Source file is processed 
in the CAM station in IPC-D-356 format. (For P-CAD PCB 
designers who do not have this format, a solution is 
suggested at the end of this article). This stage is 
reliable as far as the software is concerned and most 
of the PCB manufacturers do not charge any extra for 
this testing and therefore it is highly recommended to 
perform such testing.

Bare Board Testing is the next stage and is a physical 
one. It is thorough and is now the best available 
method to ensure maximum quality of the boards 
manufactured. The Bare Board Testing is done by 
creating a test ficture for which the source is the 
IPC-D-356 format. This testing is a one-time expense 
which verifies that the PCB production is not damaged.

This issue is also addressed by Norman S. Einarson in 
his new book "Bare Board PWB Design Manual" published 
by Printed Circuit Technology in 1995. For more 
information contact P.O.Box 334, Burlington, MA 01803, 
Tel: (617) 272-0938.

Regarding P-CAD users, an Elcad utility which enables 
creating an IPC-D-356 format from the PCB file is 
available through RoyoCAD. Tel: (909) 946-7667 or 
contact Giyora Kimhi via e-mail: 
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Giyora Kimhi
Elcad Ind 91 Ltd
Tel : 011-972-3-967-6247  Fax :011-966-0948